Calcium hypochlorite is a chemical compound with formula Ca(ClO)2
. It is widely used for water treatment and as a bleaching agent (bleaching powder). This chemical is considered to be relatively stable and has greater available chlorine than sodium hypochlorite (liquid bleach).
It is manufactured using the calcium process or the sodium process.
+ 2 Cl2
+ 2 H2
+ 3 Cl2
+ 2 NaOH → Ca(OCl)2
+ 2 H2
O + 2 NaCl
Bleaching powder is actually a mixture of calcium hypochlorite Ca(OCl)2
and the basic chloride CaCl2
O with some slaked lime, Ca(OH)2
It is a yellow white solid which has a strong smell of chlorine. Calcium hypochlorite is not highly soluble in water. For that reason it should preferably be used in soft to middle hard water. There are two types of calcium hypochlorite - a dry form and a hydrated form. The hydrated form is safer to handle.
Calcium hypochlorite reacts with carbon dioxide to form calcium carbonate and release chlorine:
- 2Ca(OCl)2 + 2CO2 → 2CaCO3 + 2Cl2 + O2
Calcium hypochlorite reacts with hydrochloric acid to form calcium chloride:
- Ca(OCl)2 + 4 HCl → CaCl2 + 2 H2O + 2 Cl2
Extreme care should be used in handling this product. Always keep in a cool dry place away from any organic material. When mixing it with water, it is safest to add the calcium hypochlorite to water. This material has been known to undergo self heating and rapid decomposition accompanied by the release of toxic chlorine gas.